Saponification of cellulose esters



Patented June 12, 19 34 PATENT OFFICE SAPONIFICATION or CELLULOSE ESTERS Camille l )reyfus, New York, N. Y., and William Whitehead, Cumberland, Md., assignors to Celaiiese" Corporation of America, a corporation of Delaware No Drawing. Application June 8, 1928, 'Serial No. 284,000

, 1i Claims.

This invention relates to the treatment of products made from or containing esters of cellulose,

and is directed particularly to an improved method of saponifying such esters of cellulose.

An object of this invention is to saponify' yarns, fabrics, films, and other materials containing inorganic esters of cellulose in such a manner that valuable products of such esters will be obtained.

Another object of this invention is to provide a proces for the saponification of inorganic cellulose ester materials whereby some of the valuable properties of the material will be enrious methods of denitrating nitro cellulose or" amount of alkali in the presence of a swelling or penetrating agent. 7

Another object of this invention is to.treat nitro cellulose in such a manner that its inflammability is greatly reduced but its other valuable (textile) properties are retained.

Another object oi this invention is to treat nitro cellulose in such a manner that its ability to absorb atmospheric humidity is greatly in- ..creased. other objects and advantages of this invention will appear from the following detailed description. f Yarns, fabrics and materials containing nitro cellulose have not been used for textiles and other purposes, except explosives, because of the very high infiammability of the nitro cellulose. Va-

' otherwise treating the same to reduce its -noninflammability have been suggested but these have Y of the cellulose nitrate is effected by the use of an alkali or its equivalent in the presence of a swelling or penetrating agent, the very nature of the saponification seems to be altered. The cellu- 5 lose and/ or cellulose ester remaining as a result of such a saponification seems to be different from that resulting from a normal saponification of a cellulose'nitrate in that itdoes not seem to be afieoted by cotton dyes. 7

In addition to this unexpected result in the condition of the cellulose resulting from our new method of saponification, it has also been found that it is possible to efiect an abnormally greater degree of saponification than is theoretically pos- 7 sible with a given amount of alkali. A saponification of aproximately 95% was obtained by utilizing only 3% sodium hydroxide, that is so much sodium hydroxide as would normally give a saponiflcation of 3% lithe saponification proceeded o quantitatively according to the theoretical equation.

Cellulose nitrate-i-sodium hydroxide=cel1ulose+ sodium nitrate This discovery is very important in view of the fact that it makes it possible to secure almost complete saponification oi the nitro cellulose regardless oi the amount or saponitying medium ipresent, provided, however, that a certain mini- 6 mum quantity of the medium is present to initiate the saponification. Theextent of saponification desired will determine the length of time for which the reaction is permitted to continue, al-

though the time is not the-sole factor. I

The cellulose nitrate materials treated in accordance with thispro'cess possessanother remarkable property, not only over materials saponified by other known methods but also over the cellulose nitrate materials in their original state. This is their remarkable increase in strength as compared with unsaponifled cellulose esters or cellulose esters saponified by theold methods. In several instances the increases in the drytensile strength of yarns treated in accordance with this invention has been as high as 35% even though the yarn had been saponified approximately 90%. I

In accordance with this invention the textile material such as yarns, fabrics or garments made no of or containing inorganic esters of cellulose, particularly cellulose nitrate, is treated with a solution containing a swelling or penetrating agent for the cellulose esters and a hydroxy compound to e'fiect the saponification. The latter need be present only in suflicient concentration to initiate the saponification process under the conditions existing in the bath. The temperature should preferably be comparatively low.

The textile material to be treated can be in any desired form such as yarn or thread in hanks or on bobbins or pirns, or it may be in the form of fabric, knitted or woven or even in the form of garments. The sapomte'd' immersing the material in a bath containing a swelling or penetrating agent and saponifying medium or the solution may be sprayed upon the material or the material may be padded with.

or impregnated with the solution for the desired period of time. Good results have been obtained by utilizing a bath in which the material is submerged or immersed. These operations can be carried out in a tank, on a jig or with any. other suitable apparatus.

Without desiring to be limited to such specific concentrations or particular reagents, it can be stated that very good results were obtained util-' izing a bath comprising 100% methanol containing enough sodium hydroxide aswould normally cause a 3% saponification of the cellulose esters. The temperature should be kept moderately low, for instance around 25 C. The time, will, of course, vary depending to some degree upon the extent of saponification desired. Thus at the end of 12 hours an approximate saponification of 95% was effected. The time could be shortened by using a higher concentration of saponifying agent as well as by using a higher bath temperature. However, the lower temperatures are preferable since they give a more uniform saponification.

The material which may be used to effect the saponification can be sodium hydroxide, potassium hydroxide, ammonium hydroxide, barium hydroxide or any other alkaline compounds which will yield hydroxyl ions under the conditions of operation, such as for example, the alkali carbonates. As examples of swelling or penetrating agents which are suitable for the purpose in hand are methyl alcohol, ethyl alcohol, phenols, glycols, polyhydric alcohols, etc. The swelling or penetrating agents selected should, of course, be-capable of dissolving the saponifying medium employed. As previously stated excellent results were obtained using sodium hydroxide as a saponifying medium and methyl alcohol as the swelling agent. Similar ,results were also obtained with ethyl alcohol and potassium hydroxide, also by solutions formed by adding metallic sodium or potassium to alcohols.

This process is applicable not only to yarns, threads, films, etc. made of or containing inorganic esters of cellulose but also to such materials when they contain mixtures of suchesters. Also it can be applied to such inorganic cellulose ester materials when they are admixed or formed with other fibres whether the latter are animal, vegetable or artificial in nature. Thus a fabric containing cellulose nitrate in admixture with cotton, wool, silk, linen, reconstituted cellulose (rayon) can be effectively treated in accordance with this invention. This treatment is particularly suitable for the treatment of mixed fabrics of silk and cellulose nitrate since the saponify- I Aurount NaOH in bath to give %s aponification o ing medium will simultaneously degum the silk and saponify the cellulose esters.

' In many instances it has been found desirable to wet the fabric or material containing the cellulose nitrate with the swelling agent alone or a dilute solution of the same before subjecting it to the saponifying process. This prior wetting of the fabric is found to result in an even saponification, no doubt due to the fact that the saponifying solution is more easily and uniformly absorbed by a wetted material than by a dry one. The fact that the cellulose remaining after v saponification according to our invention is difd cel1ulose isiuk% ther evidenced by the increase in strength noted in the saponified yarn. As previously stated this increase in strength in many instances ranges as high as 35%. Thus a yarn which was saponified over 95% was found to have an increased breaking strength and extensibility, taking into consideration that its denier has been very greatly reduced by the saponification. This indicates that while there has been a loss of nitro radicals in the cellulose molecules there has only been a slight loss of bonds between the cellulose molecules themselves which form the yarn, a result quite opposite to that resulting from normal saponification.

The following examples are given to further illustrate our invention but without any desire to limit ourselves to-such specific examples.

Example I 50 grams of nitro cellulose yarn were treated in a bath of equal parts of methyl alcohol and water containing dissolved sodium hydroxide. The bath was 20 times the weight of the yarn, the time of treatment was 12 hours and the bath was maintained at a temperature of approximately 25 to 30 C. with the following results:

mtnounl; NaOH to give saponifica'- Example II 50 grams of cellulose nitrate yarns were treated as outlined in Example I substituting a bath of 3 parts of methyl alcohol and 1 part of water. The following resultswere obtained.

Amount NaOH to give saponification of Actual saponification as NO;

groups lost 0.5 l. 0 Actual saponification as NO;.grou ps lost 39. 2 81. 9 9

In the above examples, the dry tensile strength of the yarn increased from 1.6, that of the blank, to 1.9 in some instances and to as high as 2.15 in other instances. This'increase in strength of the yarn is entirely unexpected and decidedly advan- Dry splm unsaponified nitrate cellulose yarn absorbs very little atmospheric moisture and is so hard and brittle that its use in textile operations in that condition is almost impossible. We have found that as a result of our invention the percentage of moisture regain of such saponifled yarn is much higher than that of unsaponifled yarn, rendering the yarn softer and more pliable and for that reason utilizable in textile opera-- tions. This increased moisture regain also serves to compensate for the loss of weight due to saponification. In some instances the percentage of moisture regain has increased from 2.5 to as high as 9.7%.

'3 While the specific description has dealt largely with cellulose nitrate, the invention is not to be considered as limited thereto but as applicable to all inorganic cellulose esters and the term cellulose esters as used in the claims is to be so interpreted.

The term percent sodium hydroxide as used.

in the description and claims means the amount of sodium hydroxide necessary to cause that percent of saponification if the reaction proceeded quantatively as follows:

Cellulose nitrate sodium hydroxide cellulose sodium nitrate The term percent of saponification as used 0 in the description and claims is calculated on the loss in dry weight and is quoted as percent of nitro groups lost, assuming an original nitro value of 51.7%. Penetrating agents, as well as swelling agents, are included within the term swelling agents" as used in the claims.

Having described our invention what we claim and desire to secure by Letters Patent is:

1. Method of saponii'ying to a predetermined degree material containing cellulose nitrate 4: which comprises treating the same, in the presence of a swelling agent, with an amount of alkaline saponifying agent less than that quantitatively equivalent to such degree of saponication and continuing the treatment until said =1; predetermined degree of saponification is at- .2 3. Method of saponifying to a predetermined degree material containing cellulose nitrate which comprises treating the same with a solution of sodium hydroxide in an alcohol, the amount of sodium hydroxide being less than that quantitativel'y equivalent to such degree of saponification and continuing the treatment until said predetermined degree of saponification is attained.

4. Method of saponifying to a predetermined .1 degree material containing cellulose nitrate which comprises treating the same with a solution of alkali in ethyl alcohol, the amount of alkali being less than that quantitatively equivalent to such degree of saponification and continuing the treatment until said predetermined degree of saponification is attained.

5. Method of saponifying to a predetermined degree material containing cellulose nitrate which comprises treating the same with an amount of alkali less than that quantitatively equivalent to such degree of saponification, the alkali being in solution in methyl alcohol and continuing the treatment 'until said predetermined degree of saponificat'ion is attained.

6. Method of increasing the tensile strength of textile materials containing cellulose nitrate which comprises saponifying such material to a predetermined degree, in the presence of a swelling agent, with an amount of alkaline saponifying agent less than that quantitatively equivalent to such degree of saponification and continuing the treatment until said predetermined degree of saponification is attained.

7. Method of increasing the tensile strength of textile materials containing cellulose nitrate which comprises saponifying such material, in the presence of methyl alcohol, with an amount of alkaline saponifying agent less than that quantitatively equivalent to such degree of saponification and continuing the treatment until said predetermined degree of saponification' is attained.

8. Method of saponifying material containing cellulose nitrate which comprises subjecting the same to the action of non-aqueous methyl alcohol containing sodium hydroxide in amounts theoretically equivalent to a 3% saponification of the cellulose nitrate for not more than 16 hours at approximately C.

9. Method of. saponifying material containing cellulose nitrate which comprises treating the same, in the presence of a swelling agent, with an amount of alkaline saponifying agent quan titatively equivalent to no more than 0.5% to 20% of saponification and continuing the treatment until at least 2.3% to 97.1% of saponification is attained.

10. Method of saponifying material containing cellulose nitrate which comprises treating the same, in the presence of a swelling agent, with an amount of alkaline sapo-nifying agent quantitatively equivalent to no more than 1% to 20% of saponifieation and continuing the treatment until at least 14.8% to 90.9% of saponification is at .tained.

11. Method of saponifying material containing cellulose nitrate which comprises treating the same with a solution of sodium hydroxide in an alcohol, the amount of sodium hydroxide present being quantitatively equivalent to about 3% of saponification and continuing the treatment until at least 95% of saponification is attained.

CAMILLE DREYFUS. WILLIAM WHITEHEAD. 

